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I am doing CMDA overhead sprinklers for in-rack class 4 storage at 15' - a new system.
As I was navigating through NFPA 13 2022 Chapter 21, I came to 21.4, which seems to be where I should be. My question is: 21.4.1.1.1 is where you start, which states that if it's a new sprinkler system, the demand shall be determined in accordance with 24.4.1.2.2.1. BUT, I skipped that and went on to 21.4.1.2.1.1, which seems to be for the EXACT SAME CRITERIA (unless I cannot read/comprehend, which is possible)! So when would you use 24.4.1.2.2.1 over 21.4.1.2.1.1? When we use 24.4.1.2.2.1 with the modification chart, we get a density of 0.297, and when we use 24.4.1.2.1.1, it calls for 0.30. So they're pretty much the same... but I'm not seeing why you would ever use 24.4.1.2.1.1 since 24.4.1.1.1 directs you to 24.4.1.2.2.1 and bypasses the other. Hopefully, this makes sense. --- 21.4.1.1 General 21.4.1.1.1 Ceiling sprinkler water demand for new systems shall be determined in accordance with 21.4.1.2.2.1 for single and double row racks or... 21.4.1.1.2 Ceiling sprinkler water demand for the modification of existing systems... 21.4.1.2 Protection Criteria for Single or Double-Row Rack Storage of Class I-IV Commodities over 12 ft Up to and Including 25 ft in Height. 21.4.1.2.1 New Systems Criteria for Single- or Double-Row Rack Storage of Class I-IV Commodities Stored Over 12 ft Up to and Including 25 ft in Height. 21.4.1.2.1.1 For single- or double-row racks for Class I, II, III, or IV commodities, encapsulated or nonencapsulated, the ceiling sprinkler demand.... shall be selected from the criteria in Table 21.4.1.2.1.1(a) through Table 21.4.1.2.1.1(c) that are appropriate for... and shall be modified as appropriate by 21.4.1.4. --- Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
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In a four-story educational building, we have a large pipe chase that wraps around the men’s and women’s restrooms on each floor. The highlighted area in the attached sketch is the pipe chase area.  The wall on the left (with the red arrows pointing at it) is a 1 hour rated shaft wall. All the other walls around the pipe chase are non-rated wall assemblies. There are doors (blue boxes) giving access to this area in three different locations. There isn’t any equipment or sources of ignition located inside the chase, just plumbing pipe.
While the area is not to be used for storage, we are concerned that the presence of the doors will allow people to do so. The Architect/Engineer has directed us not to protect this area with sprinklers. Are sprinklers required inside this chase or can they be omitted as directed by the A/E? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I'm working on a fire protection design for a new apartment building. The architect is adding what they're calling horizontal exits throughout the building, which will increase the number of required standpipes per the local building code (IBC-based, 2025) Section 905.4. Per the exception to 905.4.2, I do not believe we will need hose connections on both sides of every horizontal exit within the building. I think additional standpipes and hose connections will only be required in the center of the building. Other than the egress stairwells, where are standpipes and hose connections required to be located? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe  Thank you all for taking the time to make the Forum a better place! We appreciate our Top March 2026 Contributors.
I have a plan reviewer requiring calculations (CFH) for a diesel fuel tank because the vent extends further than the UL label is calculated for.
What are the guidelines and how is this calculation performed? The comment: "Provide the required emergency vent capacity, in Cubic Feet Per Hour (CFH), for the primary and secondary fuel tank emergency vents. The venting capacity should be indicated on the UL label on fuel tank. The shop drawings don't list the emergency vent capacity. Note: The capacity listed on the UL label is calculated with the vent within 12 inches of the tank body. If the vent is extended above the tank more than 12-inches, additional calculations are required to account for the additional piping and height above the fuel tank. These calculations are required to be computed by a registered engineer." Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe I have a client with a 10-story office building/parking garage, a fire pump in the below-grade level, and a combined wet standpipe with a manifold on the roof for testing. The building is getting some age on it, and when performing a flow test from the roof manifold, the roof drains will leak water into the top floor offices.
The question that was posed to me by the building manager was, "Can we tie into the bottom of the standpipe and run a new test connection to the outside at ground level?" Shooting the water over the side of the building is not really an option, doable, yes, but not really an option. Just wanting some thoughts on this, my initial response was no, but then I had never been posed with this question either. If not, is it possible to permanently tie somewhere else, or conduct the test in a different way? Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe NFPA 14 requires PRV redundancy when more than two hose connections are supplied downstream of a PRV.
Does NFPA 13 have a similar requirement for sprinkler systems, or can multiple sprinkler systems be controlled by a single PRV? We are proposing to feed a riser manifold controlling (6) sprinkler systems to be supplied by a single ORV without a redundant loop. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe NFPA 13 Section 16.2.4 concerning protective coverings for sprinklers only references spray booths and mixing rooms.
I have a building that produces particulates in the air (a chip and tortilla factory). The concern is that we replace these sprinklers, and they will quickly need to be replaced again in a couple of years (96 total). I want to put on cellophane bags to protect them. The existing sprinklers are standard response. I plan to go to the AHJ for their approval, but I wanted to get the opinion of others who may have experienced something like this. Thank you in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe Can a fire pump test report be used in place of a hydrant flow test?
For an existing building, a fire pump flow test has to be done annually. It should include all the information a hydrant flow test provides to perform a hydraulic calculation for an existing building modification. Is there any code basis for taking this approach? I have an AHJ that keeps pushing back on this approach for determining the water supply information. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe |
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